DESCRIPTION (adapted from the application): The function of the Mass Spectrometry Core is to provide a state-of-the-art laboratory facility for the purpose of enhancing the use of stable isotopes in nutrition research. This research will help us develop an understanding of nutrient absorption, metabolism, and turnover. Specifically, the core will be involved in mineral metabolism (mineral enrichment methodologies including modeling); measuring enrichments in biomolecules that will be sued to detect bioconversion and metabolism; gas isotope ration determinations for total energy expenditure (TEE); gas isotope ratio determinations for substrate oxidation. The Mass Spectrometry center has a long standing history at the University of Colorado Health Sciences Center, and served as an NIH Research resource facility for more than 12 years (until 1991). Through the strong bridging support of the School of Medicine and the Department of Pediatrics, we have maintained the Mass Spectrometry facility and its expert staff. The CNRU grant has provided new equipment for this core and has helped to stabilize the salary support for the most important human resources of this core. The Mass Spectrometry Core laboratory provides access to a number of state of the art mass spectrometers and trained personnel who can assist each investigator to effectively plan and implement their specific research project. This core provides an instrument (VG 7070H) and corresponding hardware for the measurement of enrichment of minerals (Fe, Cu, and ZN); three instruments (MSDs) that are dedicated to the measurements of stable isotopes in simple biomolecules (amino acids, sugars, and fats); an instrument (HP 5989A Engine) is used for developmental assays and measurement of specific target compounds; and a VG Optima gas isotope ratio mass spectrometer for both enriched CO2 and 2H determinations. However, the high expense of this equipment and the complexity of its maintenance make it impossible for an single investigator to function independent of the center. Thus, this is clearly an example of a core which extends and enhances the research opportunities of the core members.